1. Field of the Invention
The present invention relates to a trailing element device for a headbox of a papermaking machine. More particularly, the present invention relates to a trailing element device which is disposed within a headbox of a papermaking machine for dampening turbulence of stock passing through the headbox.
2. Information Disclosure Statement
The CONVERFLO headbox design reduces turbulence of stock flowing through a headbox. CONVERFLO is a registered trademark of Beloit Corporation.
More particularly, the CONVERFLO headbox includes a plurality of trailing element devices disposed within a slice chamber of a headbox. Each of the trailing element devices is pivotally anchored at an upstream end of the slice chamber, such that the respective downstream ends of the trailing element devices freely float within the slice chamber.
By the aforementioned means, as the stock passes through the slice chamber in a converging path towards the slice lip thereof, the trailing element devices are permitted to move relative to each other, thereby dampening or attenuating turbulence within the headbox so as to achieve micro-turbulence within the ejected stock. Such micro-turbulence assists in providing a more uniform web. Additionally, such micro-turbulence maintains a more uniform basis weight across the width of the resultant web.
Such trailing element devices are typically anchored within the slice chamber by means of a dove-tail or triangular shaped slot defined by the upstream end of the slice chamber. The upstream end of each trailing element device is provided with an upstream bead or enlargement such that when the trailing element device is loaded into the slice chamber, the bead is anchored within the dove-tail slot, thereby allowing the trailing element device to be substantially anchored while permitting the downstream end of the trailing element to freely float within the headbox.
In practice, it has been found that due to the movement of the bead within the slot, wear and fracturing of the trailing element device has resulted.
Such wear has particularly occurred where different grade stocks have been applied to opposite sides of the trailing element device, such as in the STRATAFLO type headbox. STRATAFLO is a registered trademark of Beloit Corporation. In the STRATAFLO type headbox, a relatively inexpensive ply of secondary stock is covered by an upper high quality ply of stock, so that the resultant web has enhanced printing characteristics and a reduced cost. Nevertheless, when such dissimilar stocks are simultaneously ejected through a STRATAFLO headbox, a pressure differential of up to 20 pounds per square inch may be applied to the trailing element device, thereby tending to fracture the element particularly where the trailing element device contacts the edges of the dove-tail slot.
The present invention seeks to overcome the aforementioned problem by providing a wear resistant cladding to the trailing element device, such that wear and fracturing of the trailing element device is inhibited.
Therefore, it is the primary object of the present invention to provide a trailing element device that overcomes the aforementioned inadequacies of the prior art devices, and to provide a trailing element device that makes a considerable contribution to the papermaking art.
Another object of the present invention is the provision of a trailing element device in which the wear resistant cladding means inhibits wear and fracturing of the sheets caused by frictional engagement between the trailing element and the anchoring slots of a headbox.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter, taken in conjunction with the annexed drawings.